Wear resistant alloy steels containing cb and one of ti, hf or zr

ABSTRACT

Alloy steels are provided with improved resistance to abrasive wear, without significantly detracting from other desired properties, by the addition of columbium and carbon to form CbC and at least one of the elements titanium, zirconium and hafnium so that an effective amount of the columbium carbide formed is idiomorphic. Specific examples are given of A.I.S.I. type H12 and type A6, and a high speed steel modified in accordance with the invention.

United States Patent Philip et a1.

1 Aug. 26, 1975 WEAR RESISTANT ALLOY STEELS CONTAINING Cb AND ONE OF Ti.Hf OR Zr.

Inventors: Thoni V. Philip, Reading, Pa;

Douglas W. Dietrich, Wyomissing Hills, Pa.

Assignee: Carpenter Technology Corporation,

Reading, Pa.

Filed: Aug. 10, 1973 Appl. No.: 387,534

Related US. Application Data Continuation-impart of Ser. No. 142,229,May 11, 1971, abandoned.

US. Cl. 75/123 H; 75/123 J; 75/123 M; 75/123 N; 75/124; 75/125; 75/126A; 75/126 B; 75/126 C; 75/126 D; 75/126 E; 75/126 F;

75/126 H; 75/128 G; 75/128 Z; 75/128 T Int. Cl. C22c 39/54 Field ofSearch 75/128 G, 128 T, 128 V, 75/128 Z, 128 A, 128 B, 128 C, 128 D, 128

N, 128 W, 128 P,124, 125,126 A, 126 B, 126 C, 126 D, 126 E, 126 F, 126H, 126 J, 126 Q, 126 L, 126 M, 123 .1, 123 M,123 H Primary Examiner-L.Dewayne Rutledge Assistant Examiner-Arthur J. Steiner Attorney, Agent,or Firm-Edgar N. Jay

[ ABSTRACT Alloy steels are provided with improved resistance toabrasive wear, without significantly detracting from other desiredproperties, by the addition of columbium and carbon to form CbC and atleast one of the elements titanium, zirconium and hafnium so that aneffective amount of the columbium carbide formed is idiomorphic.Specific examples are given of A181 type H12 and type A6, and a highspeed steel moditied in accordance with the invention.

28 Claims, 5 Drawing Figures PATENTEU AUE26 I975 FIG.3

FIG

FIG-4 INVENTOR.

ATTORNEY WEAR RESISTANT ALLOY STEELS CONTAINING CB AND ONE OF TI, HF ORZR This application is a continuation-in-part of our copendingapplication filed May 1 1, 1971, Ser. No. 142,229, and now abandoned.

This invention relates to alloy steel containing at least about 65% ironand, more particularly. to such steel containing columbium carbidehaving improved resistance to abrasive wear.

1n Fetzer and Post US. Pat. No. 2,450,888, granted Oct. 12, 1948 andassigned to the assignee of the present application, there is disclosedalloy steel containing columbium carbide characterized by improvedabrasive wear resistance. In accordance with the invention of thatpatent, the alloy steels (generally understood to include a wide varietyof steels such as hot-work steels, quench-hardenable steels,shock-resistant steels and others) are improved as to resistance toabrasive wear by the presence of columbium carbide therein. US. Pat. No.2,450,888 teaches utilizing varying amounts of columbium carbidedepending upon the amount of carbon present in the alloy matrixuncombined as columbium carbide; the amount of columbium carbide is torange from about 1.5% to 2.0% for a matrix carbon content of about1.50%, and as the amount of matrix carbon present decreases to about0.30%, the range of the amount of columbium carbide to be incorporatedin the steel increases to from 3.6% to 4.5%. However, for reasons whichwere not fully understood, consistent results could not always beobtained and, particularly in the case of when the larger amounts ofcolumbium carbide were used, the alloy tended to become objectionablybrittle.

A discovery we have made which has inspired the present invention isthat of two possible forms of columbium carbide that can be formed whencolumbium and carbon in the proper proportions are incorporated in thesteel, only idiomorphic columbium carbide seems to improve resistance toabrasive wear. And, also in accordance with the present invention, ithas been found that the presence of a small but critical amount of atleast one of the elements titanium, zirconium or hafnium serves toinsure that at least an effective amount of the idiomorphic type ofcolumbium carbide is formed during solidification of the steel.

It is therefore a principal object of this invention to provide alloysteel having consistently improved resistance to abrasive wear withoutobjectionably affecting other desired properties of such steel.

A more specific object is to provide such steel having improvedresistance to abrasive wear due to idiomorphic columbium carbidedistributed throughout the steel and formed in situ in the presence ofcarefully controlled additions of at least one of the elements titanium,zirconium or hafnium.

The foregoing as well as additional objects and advantages of thisinvention will be apparent from the following detailed description ofpreferred embodiments thereof and the accompanying drawing in whichFIGS. l-3 are micrographs showing A.I.S.l. type H 12 alloy at 250magnification modified by the addition of carbon and columbium and with0.01%, 0.05% and 0.09% titanium respectively; and

FIGS. 4 and 5 are micrographs showing A.l.S.1. type A6 at 250magnification similarly modified with carbon and columbium, and withresidual titanium and with 0.05% titanium, respectively.

The present invention stems from the discovery that columbium carbideserves to enhance the abrasive wear resistance of steel only when it ispresent in the steel in the idiomorphic form. Generally stated, inaccordance with the present invention effective amounts of columbium andcarbon together with at least one element selected from the group of0.040.3% titanium, 0.05-0.5% zirconium, and 0.03-0.5% hafnium are addedto plain carbon steels and alloy steels so that effective amounts ofidiomorphic columbium carbide are formed in the steel as it solidifiesfrom the molten state to provide improved resistance to abrasive wear.The preferred range for titanium is 0.05% to 0.15%, for zirconium 0.05%to 0.2%, and for hafnium 0.1% to 0.25%. Here and elsewhere throughoutthis application, proportions in percent are intended as weight percent.

By plain carbon steels is meant those steels whose properties aredetermined primarily by the carbon content thereof which may range fromabout 0.1% to 2%. Various elements may be present incidental to thesteelmaking process, usually small amounts of manganese up to about0.4%, aluminum when used as a deoxidizer usually less than about 0.25%,and silicon less than about 0.4%. Certain plain carbon steels maycontain as much as 1.65% manganese though not considered an alloy steel.Other elements may be present in residual or incidental amounts, as forexample, up to about 0.04% phosphorus, up to about 0.05% sulfur, up toabout 0.2% chromium, up to about 0.25% nickel, up to about 0.1%molybdenum, up to about 0.15% tungsten, up to about 0.1% vanadium, up toabout 0.15% cobalt, and up to about 0.3% copper.

When additional amounts of those elements, other than carbon, areincluded in steel so as to affect its properties, then the steel istermed an alloy steel which, in addition to a minimum of about 65% iron,0.07% to 2.5% carbon and the nominal amounts of manganese and siliconpresent in such steels, may contain up to about 2.5% manganese, up toabout 2.5% silicon, and aluminum up to about 1.5%, and, depending uponthe properties desired, one or more of up to about 19% chromium, up toabout 5% nickel, up to about 10.5% molybdenum, up to about 20% tungsten,up to about 6% vanadium, up to about 15% cobalt, up to about 0. 1%nitrogen, and up to about 4% copper.

Columbium is an essential constituent of the present composition and ispresent from about 1.1% to less than 3%. Above about 3% columbium andwith the corresponding amount of carbon, the results tend to beinconsistent while above about 3.25% embrittlement as a result ofcarbide segregation may result. Therefore, it is preferred to use nomore than about 2.99% and better yet no more than about 2.85% columbium.In addition to columbium, there is added carbon in the approximatestoichiometn'c proportions required to form columbium carbide (CbC) inthe steel. That amount of carbon is in addition to the carbon typicallypresent in the particular steel, but the total is no more than themaximum amounts previously stated of about 2.5% for wrought steels and3% for castings. When free machining properties are desired, the usualfree machining additives may be included such as, for example, one ormore of sulfur, selenium, lead, or tellurium, up to a total of 0.5%.Normally sulfur and also phosphorus are present in no more thanincidental amounts, that is less than about 0.025% although, in certainsteels. as much as about 0.25% phosphorus may be included.

No special procedures or precautions need be observed in producing thesteels of the present invention characterized by improved resistance toabrasive wear. It is sufficient that the steel be made and processed aswould be customary for the same composition absent the columbium pluscarbon addition and the addition of titanium, zirconium or hafnium but,as is well known, deoxidation should be completed before such elementsas Ti, Zr or Hf are added. As was noted, columbium and carbon are addedsubstantially in stoichiometric proportions with the amount of carbonthus added being in addition to that usually present in the steel. Inpractice, to avoid increasing the matrix carbon, that is the amount ofcarbon not tied up by the columbium. it is best to maintain theproportion of columbium somewhat in excess of the amount required tocombine stoichiometrically with the additional carbon. In practice,about 0.12% carbon for each 1% of columbium seems to give best results,but as little as 0.10% carbon for each 1% of columbium can also be used.ln other words, the ratio of the amount of columbium to the amount ofcarbon added to a given steel can vary from about 7.75 to l to about 10.to 1.

From the foregoing, it is apparent that the minimum amount of carbonpresent in the steel of this invention is about 0.07% plus the amount ofcarbon required to lumbium. Using the preferred proportions of 0.12%carbon for each 1% of columbium, the minimum carbon content is seen tobe about 0.2%. Since the amount of columbium added to the steel does notexceed about 2.99%. and preferably no more than about 2.85%, thecompositions are not embrittled.

As a more specific illustration of the present invention, fourexperimental vacuum induction heats (about 17 pounds each) were preparedand cast as split heats into 2 ingots each weighing about 7.5 pounds andhaving the following analysis:

tests referred to herein, unless otherwise indicated,

each specimen was mounted in the test apparatus so as to be held fixedin a holder against the surface of an abrasive paper under a constantload of 5 pounds, the paper being mounted on a circular disc. While theabrasive paper is rotated, the holder carrying the specimen is traversedback and forth across the surface of the paper so that substantially theentire available surface of the paper is utilized. in order to helpstandardize the results, each specimen was subjected to an initialbreak-in period of at least 1,000 revolutions, whereupon the specimenwas weighed, remounted in the holder and brought up to a fresh abrasivepaper. Throughout these procedures, the abrasive disc was rotated at 24revolutions per minute, and the abrasive paper utilized was a carefullycalibrated 120 grit alumina paper. The test itself consisted of 250revolutions of the paper against the end of the specimen under theconditions stated. Following this, the specimen was recombine with l.l7zcolumbium, the minimum of co- 3U Weighed to determine the weight 1055'The average of what was considered to be a sufficient number of tests onone or more samples was determined and is reported in Table".

The specimens of Exs. l and 2 were heat treated by heating to l850F,quenching in oil followed by heating at l l25F for 2 hours, cooling inair, and then heating for 2 hours at l lO0F and cooling in air. Thespecimens of Exs. 3-5, 7 and 8 were also quenched in oil from 1850F, butwere subjected to two 2-hour periods at 40 l l00F each followed bycooling in air. In the case of Ex.- 6 after quenching in oil from 1850F,three 2-hour TABLE I Example No.

C .7) 80 .78 .80 Mn .5l .47 .50 .47 .4) .41 .4) .46

Si L00 .QX .9) .95

S .006 .003 .004 .002 (r 4.98 4.96 4.98 4.97 4.97 4 00 4.96 4.95 Ni .03.02 .0l .02 Mu l.5l 1.50 I.5l 1.4) L52 L55 1.52 l.50 W L41 L35 L44 1.431.42 L42 1.45 1.3) .25 .25 .26 .26 .26 .21 .26 .26 (h 2.50 2.52 2.552.57 2.56 2.55 2.54 2.4) Al* .02 .02 .02 .03 .02 .02 .()l .()l TH .01.03 .05 .0) .I7 .28 .35 .40

About 0.07: aluminum as added to ensure complete klLU.\lklZ\llt ll befre 'li was added to the melt.

In each of Examples l-8, the balance was iron and periods at ll00F eachfollowed by cooling in air were incidental impurities. The dashes in theeven-numbered examples indicate that it was not considered necessary tomake a second analysis for C, Si, P, S and Ni in the second half of eachof the split heats.

Each of the ingots of Examples l-8 was 2 /4 inch sq. They were eachforged from a furnace temperature of 2150F to 1 inch square bars andthen buried in vermiculite and cooled. The forged bars were packedanused.

TABLE ll Hardness Average Wt. No. of Fax. No. X Ti (R,.) Loss. GramsTests l .0l 47.5 .457 I0 TABLE II-Continued Hardness Average Wt. No. ofEx. No. 7: Ti (R,.) Loss. Grams Tests Except for the added carbon andcolumbium, Ex. 1 corresponds to the well-known A.I.S.I. type H12 alloy,a hot work tool and die steel. The nominal carbon content of type H12 isusually 0.35% Thus. the carbon content of about 0.8% in Exs. l-8 is seento be about 0.15% more than the 0.65% preferable for the columbiumcontent of approximately 2.5% present in these examples. For the amountof columbium, the stoichiometric proportion of carbon to be added toreact with the columbium would be close to 0.3%. However, ex cept forthe increase in the hardness level, the added carbon had no significanteffect as is apparent from the deviation in hardness of only plus orminus 0.5 R}, and the abrasive wear resistance test data of the variousex amples given in Table II can be directly compared. The data in Table11 clearly demonstrates the sharp criticallity of a small amount oftitanium. With 0.01% and 0.03% titanium, there was no apparent effect onthe abrasive wear resistance. FIG. 1 is a micrograph prepared from aspecimen of Ex. 1 Except for the columbium carbides in the form of moreor less rod-shaped or lamellar allotriomorphic crystals, themicrostructure is believed to be typical of and not significantlydifferent from what would be expected of such a composition afterforging. While the microstructure of Ex. 2 with 0.03% titanium is notillustrated in the drawing, it does not differ significantly from thatshown in FIG. 1 and contained only a few widely scattered idiomorphiccolumbium carbides. With 0.05% titanium, Ex. 3 shows a sharp averagereduction in weight loss down to 0.207 grams as an average of tests andwith the same hardness, R 475 as Exs. 1 and 2. Numerous tests andstudies have demonstrated that the small but effective amount oftitanium, about 0.04% preferably 0.05%, radically affects the morphologyof the columbium carbide crystals in a way which is not fullyunderstood. But the apparent effect is the formation of the angular,idiomorphic columbium carbides, several of which are visible near thecenter of FIG. 2. An even larger number of idiomorphic columbiumcarbides is visible in the micrograph of FIG. 3. At about 0.2% titaniumand above all the columbium carbide present in the compositions testedappears to be in the form of idiomorphic carbides. It has also beenfound that in each of the Exs. 28 the number of idiomorphic columbiumcarbides increased as the titanium content was increased with theindividual carbides decreasing in size and becoming more uniformlydistributed. It is therefore hypothesized that the titanium wasprecipitated probably as titanium carbide and caused nucleation of thecolumbium carbides early enough in the solidification of the melt sothat, being free to grow unrestrained, the idiomorphic crystals wereformed. y

From the data in Table II, it is apparent that in each of the Exs. 3-8there was a substantial improvement in resistance to abrasive wear asmeasured by the test described. However. as will be seen, with 0.35% and0.40% titanium respectively, Exs. 7 and 8 showed embrittlement due tocarbide segregation. For this reason, titanium is limited to about 0.3%and preferably to about 0.15%.

It may be well to note that the idomorphic columbium carbides aregenerally cubic in form; much of the differences in the idiomorphiccolumbium carbides apparent in the drawing are primarily the result ofvariations in orientation of the carbides with respect to the plane ofthe micrographs.

Standard room temperature tensile test specimens were prepared having agauge diameter of 0.252 in. and a gauge length 4 times the gaugediameter. They were heat treated as was previously described for eachexample except that the specimens of Ex. 6 received the same heattreatment as Exs. 3-5, 7 and 8. The results of these'tests together withthe hardness of the specimen as tested are set forth in Table III as theaverage of two tests except for Exs. 1, 7 and 8. In the case of Ex. 1,only one test specimen was available. In the case of Exs. 7 and 8, twospecimens were tested, but one specimen of each pair failed with lowductility, less than 4% elongation and less than 1 1% reduction in areabecause of columbium carbide segregation. In Table III, the 0.2% yieldstrength (0.2% vYS) and the ultimate tensile strength (UTS) are given inunits of 1,000 pounds per square inch (ksi) as indicated. Percentelongation (7b El) and percent reduction in area Ra) are also given.

These results indicate that the tensile properties are not significantlyaffected by the presence of idiomorphic carbides and with columbium atthe level of about 2.5% tested, tensile ductility is improved ascompared to the tensile ductility of such a composition but with as muchas 3.5% columbium. It should also be observed that with no more thanabout 0.3% titanium, the tensile properties were adequate for most, ifnot all, customary uses A.I.S.I. type H12.

Thus, one preferred composition of the present invention consistsessentially of of about 0.45% to 0.9% carbon (the total of matrix carbonand that in the form of carbides), a maximum of 0.6% manganese, about0.75% to 1.25% silicon, about 4% to 5.5% chromium, about 1% to 1.7%molybdenum, about 1% to 1.7% tungsten, about 0.2% to 0.6% vanadium,about 2% to 2.75% columbium, at least one element selected from thegroup of 0.04% to 0.15%, preferably 0.05% to 0.15%, titanium, 0.05% to0.2% zirconium, and 0.03% to 0.5%, preferably 0.1% to 0.2%, hafnium, andthe balance essentially iron and incidental impurities. This will berecognized as A.I.S.I. type H12 modified in accordance with the presentinvention. This composition, like H12, is suited for use as a hot workdie steel and because of its substantially greater resistance to abra-TABLE IV Ex. No. C Mn Si Cr Mo Ch Ti Example 9 will be recognized asA.I.S.l. type A6 alloy modified in accordance with the presentinvention. I

The heats were cast as 1% in. sq. ingots which were forged to l A; in.sq. billets from a furnace temperature of 2050F and then buried invermiculite to cool. The billets were pack annealed at 1400F for 4hours, cooled F per hour to 1000F and then air cooled. The annealedhardnesses obtained were R,,98.599.5. Wear test specimens of the typedescribed in connection with Exs. 1-8 were prepared from the billets ofExs. 9 and 10, and the specimens were then heated at 1550F for 3minutes, air cooled and then tempered at 350F for 1 hour. Because of thehardness of these specimens, the abrasive wear test was modified toensure that the abrasive paper was not worn out prematurely and wouldcontinue to abrade each specimen throughout each test. The modified testconsisted of determining the weight loss in grams after 500 revolutionswith a fresh abrasive paper being used after each 100 revolutions. Theother conditions of the test were the same as those previously noted.The average weight loss from 3 tests, the titanium content and thehardness of the specimens are given in Table V.

amount of titanium which, with the columbium and carbon, provides asynergistic effect.

Thus, another preferred composition of the present invention consistsessentially of about 0.4% to 1.2% carbon (matrix carbon plus carbides),about 0.5% to 2.5% manganese, about 0.5% to 1.5% chromium, about 0.25%to 1.75% molybdenum, about 1.1% to 2.99%, preferably 2.5% to 2.85%,columbium, at least one element selected from the group of 0.04% to 0.3%preferably 0.05% to 0.15% titanium, 0.05% to 0.5% preferably 0.05% to0.2% zirconium, and 0.03% to 0.5% preferably 0.1% to 0.25% hafnium, andthe balance essentially iron and incidental impurities.

Referring once again to FIGS. 4 and 5, it is apparent that, even in theabsence of a titanium addition, some idiomorphic columbium carbides toosmall to be effective are formed. As the columbium is increased to 3% inthe composition of Ex. 10, more larger idiomorphic carbides are formed,but the addition of titanium with columbium less than 3% affects themorphology of the columbium carbide sufficiently to provide a small butdefinite improvement in abrasive wear resistance.

A.I.S.l. type A6 alloy modified in accordance with this invention,Example 9, is a deep air-hardening alloy steel suitable for a widevariety of cold-work uses such as in blanking and coining and for use asthread rolling dies and trimming dies. It is well suited for such usesand others because of its improved resistance to abrasive wear without asignificant loss in ductility.

Other modifications will be apparent to those skilled in this art. Forexample, in the case of A.I.S.l. type H12 as modified in accordance withthe present invention, reduction of the tungsten content to no more thana residual amount of less than about 0.15% gives A.I.S.l. type H1 1modified according to this invention. Further, when about 0.85% to 1.25%vanadium is included in the thus modified type H1 1, the result isA.I.S.l. type H13 modified in accordance with this invention.

As an additional illustration of this invention, two 5- poundexperimental air induction heats of a high-speed steel were melted tothe analyses indicated in Table VI, the balance in each case being ironand incidental impurities. To ensure complete deoxidation before theTABLE V addition of the titanium, 0.10% aluminum was added to each heat,as in Examples 9 and 10.

Average Weight Ex. No. 7: Ti Hardness (R,.) loss. Grams TABLE VI 9 .0501.0 .154 10 5.01 61.0 .376 EX 11 Ex [2 Carbon 0.89 0.86 Manganese 0.01().()1 Example 9 containing 0.05% titanium in accordance silicon (H0 (H9with the present invention lost an average of only 0.154 ghrfrnium K: 'egrams as compared to an average weight loss for Ex. 10 H Molybdenum 5 54l 3 of 0.376 grams from essentially the same analysis as Ex. gobult 8.0211.20 .r 1.0- 1.00 9 but with only residual titanium Referring to FIGS.4 088 02 and 5, the very great difference in the form of the co-Columbium 2.34 2.44 Aluminum 0.02 0.05 lumbium carbides can be clearlyseen. The few small Titanium (m7 Um idiomorphic carbides that can beseen in the mICI'O- graph of FIG. 4 prepared from Ex. 10 reflect thefact that there was not an effective amount of titanium present. ln thecase of the micrograph of Ex. 9 shown in FIG. 5, the more numerous andlarger idiomorphic carbides are clearly seen which provide the improvedre sistance to abrasive wear. As in the case of Exs. l8, the sharpdifference between Exs. 9 and 10 clearly demonstrates the criticallityof the small but effective TABLE VII Hardness Average Weight Ex. No. 7:Ti (R f) Loss. Grams Example 1 1 containing 0.07% titanium, inaccordance with the present invention, lost an average of only 0.0324grams. Example 12, from essentially the same analysis as Example 1 l,but with only 0.01% titanium, had a much larger average weight loss of0.0797 grams. Examination of the microstructure of Examples 1 1 and 12showed that Example 1 1 has more numerous and larger idiomorphic carbidecrystals than Example 12. Examples 1 1 and 12 clearly show, as didExamples 1-10, the synergistic effect of a small but critical amount oftitanium which, when added with the columbium and carbon, providesimproved resistance to abrasive wear.

Thus, another preferred composition of the present invention consistsessentially of about 0.5% to 2.0% carbon (matrix carbon plus carbides),less than about 0.5%, preferably about 0.15% to 0.4% manganese, lessthan about 0.5%, preferably about 0.15% to 0.4% silicon, about 3.5% to4.5% chromium, a maximum of about 0.5% nickel, up to about 19% tungsten,up to about 10% molybdenum, a maximum of about 0.5% copper, 0.75% to5.5% vanadium, about 3% to 12% cobalt, a maximum of about 0.1% nitrogen,about 1.1% to 2.99%, preferably 2.5% to 2.85%, columbiurn, at least oneelement selected from the group of 0.04% to 0.3%, preferably 0.05% to0.15%, titanium, 0.05% to 0.5%, preferably 0.05% to 0.2%, zirconium, and0.03% to 0.5%, preferably 0.1% to 0.25%, hafnium, and the balanceessentially iron and incidental impurities.

The terms and expressions which have been employed are used as terms ofdescription and not of limitation, and there is no intention in the useof such terms and expressions of excluding any equivalents of thefeatures shown and described or portions thereof, but it is recognizedthat various modifications are possible within the scope of theinvention claimed.

We claim:

1. Alloy steel consisting essentially by weight of about 0.2% to 2.5%carbon, up to about 2.5% manganese, up to about 2.5% silicon, up toabout 1.5% aluminum, up to about 19% chromium, up to about 5% nickel, upto about 10.5% molybdenum, up to about 20% tungsten, up to about 6%vanadium, up to about cobalt, up to about 4% copper, up to about 0.1%nitrogen, about 1. 1% to 2.99% columbium, at least one element selectedfrom the group consisting of 0.04% to 0.3% titanium, 0.05% to 0.5%zirconium and 0.03% to 0.5% hafnium, the balance iron and incidentalimpurities, the iron content being at least 65%, the amount of carbonbeing at least about 0.07% plus the amount required to combine with thecolumbium to form columbium carbide, and said one element beingeffective to increase the amount of idiomorphic columbium carbide formedwhereby said steel has improved resistance to abrasive wear.

2. The steel set forth in claim 1 further containing up to about 0.5% ofat least one additive selected from the group consisting of sulfur,selenium, lead and tellurium.

3. The steel set forth in claim 1 in which said one element is about0.04% to 0.15% titanium.

4. The steel set forth in claim 1 in which said one element is about0.05% to 0.2% zirconium.

5. The steel set forth in claim 1 in which said one element is about 0.1to 0.25% hafnium.

6. The steel set forth in claim 3 which contains about 1.1% to 2.85%columbium.

7. The steel set forth in claim 4 which contains about 1.1% to 2.85%columbium.

8. The steel set forth in claim 5 which contains about 1.1% to 2.85%columbium.

9. Abrasive wear resistant hot work steel consisting essentially byweight of about 0.45% to 0.9% carbon, no more than about 0.6% manganese,about 0.75% to 1.25% silicon, about 4% to 5.5% chromium, about 1% to1.7% molybdenum, up to about 1.7% tungsten, about 0.2% to 1.25%vanadium, up to about 0.1% nitrogen, about 2% to 2.75% columbium atleast one element selected from the group consisting of 0.04% to 0.15%titanium, 0.05% to 0.2% zirconium, and 0.03% to 0.5% hafnium, thebalance consisting essentially of iron and incidental impurities, theamount of carbon being at least about 0.07% plus the amount required tocombine with the columbium to form columbium carbide, and said oneelement being effective to increase substantially the amount ofidiomorphic columbium carbide formed whereby said steel has improvedresistance to abrasive wear. 1

10. The abrasive wear resistant hot work steel set forth in claim 9 inwhich said one element is about 0.05% to 0.15% titanium.

11. The abrasive wear resistant hot work steel set forth in claim 9which said one element is about 0. 1% to 0.25% hafnium.

l2. Abrasive wear resistant deep air-hardening steel consistingessentially by weight of 0.4% to 1.2% carbon, about 0.5% to 2.5%manganese, about 0.5% to 1.5% chromium, about 0.25% to 1.75% molybdenum,up to about 0.1% nitrogen, about 1.1% to 2.99 columbium, at least oneelement selected from the group consisting of 0.04% to 0.3% titanium,0.05% to 0.5% zirconium, and 0.03% to 0.5% hafnium, the balanceconsisting essentially of iron and incidental impurities, the amount ofcarbon being at least about 0.07% plus the amount required to combinewith the columbium to form columbium carbide, and said one element beingeffective to increase the amount of idiomorphic columbium carbide formedwhereby said steel has improved resistance to abrasive wear.

13. The abrasive wear resistant deep air-hardening steel set forth inclaim 12 which contains about 1.1% to 2.85% columbium.

14. The abrasive wear resistant deep air-hardneing steel set forth inclaim 13 in which said one element is 0.05% to 0.15% titanium.

15. The abrasive wear resistant deep air-hardening steel set forth inclaim 13 in which said one element is 0.05% to 0.2% zirconium.

16. The abrasive wear resistant deep air-hardening steel set forth inclaim 13 in which said one element is 0.1% to 0.25% hafnium.

17. The abrasive wear resistant deep air-hardening steel set forth inclaim 14 which contains about 2.5% to 2.85% columbium.

18. The abrasive wear resistant deep air-hardening steel set forth inclaim 15 which contains about 2.5% to 2.85% columbium.

19. The abrasive wear resistant deep air-hardening steel set forth inclaim 16 which contains about 2.5% to 2.85% columbium.

20. Abrasive wear resistant high speed steel consisting essentially byweight of about 0.5% to 2.0% carbon, less than about 0.5% manganese,less than about 0.5% silicon, about 3.5% to 4.5% chromium, up to about0.5% nickel, up to about 10.5% molybdenum, up to about 19% tungsten,about 0.75% to 5.5% vanadium, about 3% to 12% cobalt, up to about 0.5%copper, about 1.1% to 2.99% columbium, up to about 0.1% nitrogen, atleast one element selected from the group consisting of 0.04% to 0.3%titanium, 0.05% to 0.5% zirconium and 0.03% to 0.5% hafnium, the balanceconsisting essentially of iron and incidental impurities, the columbiumand some of the carbon forming columbium carbide, and said one elementbeing effective to increase the amount of idiomorphic columbium carbideformed whereby said steel has improved resistance to abrasive wear.

21. The abrasive wear resistant high speed steel set forth in claim 20which contains about 0.15% to 0.4% manganese and about 0.15% to 0.4%silicon.

22. The abrasive wear resistant high speed steel set forth in claim 20which contains 1.1% to 2.85% columbium.

23. The abrasive wear resistant high speed steel set forth in claim 22in which said one element is about 0.05% to 0.15% titanium.

24. The abrasive wear resistant high speed steel set forth in claim 22in which said one element is about 0.05% to 0.2% zirconium.

25. The abrasive wear resistant high speed steel set forth in claim 22in which said one element is about 0.1% to 0.25% hafnium.

26. The abrasive wear resistant high speed steel set forth in claim 23which contains about 2.5% to 2.85% columbium.

27. The abrasive wear resistant high speed steel set forth in claim 24which contains about 2.5% to 2.85% columbium.

28. The abrasive wear resistant high speed steel set forth in claim 25which contains about 2.5% to 2.85%

columbium.

UNITED STATES PATENT OFFICE QERTHHCATE OF CORRECTTON PATENT NO. 33190].,690

DATED 1 August 26, 1975 INVENTOMS): Thoni V. Philip and Douglas W.Dietrich Itis cerflfiedthat enor appears n1the above-ddentfiiedpatentand thatsaidl eflers Patent mehadwcmmcmdasdwwnbdow Col. 3, TableI, in line "C", under the subheading "3",

for "80" read .80 line 68, for "packed" read pack Col. 5, line 19, after"For", for "the" read that Col. 6, line 52, after "uses" insert of line54, delete the second occurrence of "of". Col. 7, line 31, for "3" read3O Col. 10, line 27, after "columbium", insert line 48, for "2.99" read2.99%

Signed and Scaled thisthirtieth D f March 1976 [SEAL] A ttest:

1. ALLOY STEEL CONSISTING ESSENTIALLY BY WEIGHT OF ABOUT 0.2% TO 2.5%CARBON, UP TO ABOUT 2.5% MANGANESE, UP TO ABOUT 2.5% SILICON, UP TOABOUT 1.5% ALUMINUM, UP TO ABOUT 19% CHROMIUM, UP TO ABOUT 5% NICKEL, UPTO ABOUT 10.5% MOLYBDENUM, UP TO ABOUT 20% TUNGSTEN, UP TO ABOUT 6%VANADIUM, UP TO ABOUT 15% COBALT, UP TO ABOUT 4% COPPER, UP TO ABOUT0.1% NITROGEN, ABOUT 1.1% TO 2.99% COLUMBIUM, AT LEAST ONE ELEMENTSELECTED FROM THE GROUP CONSISTING OF 0.04% TO 0.3% TITANIUM, 0.05% TO0.5% ZIRCONIUM AND 0.03% TO 0.5% HAFNIUM, THE BALANCE IRON ANDINCIDENTAL IMPURITIES, THE IRON CONTENT BEING AT LEAST 65%, THE AMOUNTOF CARBON BEING AT LEAST ABOUT 0.07% PLUS THE AMOUNT REQUIRED TO COMBINEWITH THE COLUMBIUM TO FORM COLUMBIUM CARBIDE, AND SAID ONEELEMENT BEINGEFFECTIVE TO INCREASE THE AMOUNT OF IDIOMORPHIC COLUMBIUM CARBIDE FORMEDWHEREBY SAID STEEL HAS IMPROVED RESISTANCE TO ABRASIVE WEAR.
 2. Thesteel set forth in claim 1 further containing up to about 0.5% of atleast one additive selected from the group consisting of sulfur,selenium, lead and tellurium.
 3. The steel set forth in claim 1 in whichsaid one element is about 0.04% to 0.15% titanium.
 4. The steel setforth in claim 1 in which said one element is about 0.05% to 0.2%zirconium.
 5. The steel set forth in claim 1 in which said one elementis about 0.1 to 0.25% hafnium.
 6. The steel set forth in claim 3 whichcontains about 1.1% to 2.85% columbium.
 7. The steel set forth in claim4 which contains about 1.1% to 2.85% columbium.
 8. The steel set forthin claim 5 which contains about 1.1% to 2.85% columbium.
 9. Abrasivewear resistant hot work steel consisting essentially by weight of about0.45% to 0.9% carbon, no more than about 0.6% manganese, about 0.75% to1.25% silicon, about 4% to 5.5% chromium, about 1% to 1.7% molybdenum,up to about 1.7% tungsten, about 0.2% to 1.25% vanadium, up to about0.1% nitrogen, about 2% to 2.75% columbium at least one element selectedfrom the group consisting of 0.04% to 0.15% titanium, 0.05% to 0.2%zirconium, and 0.03% to 0.5% hafnium, the balance consisting essentiallyof iron and incidental impurities, the amount of carbon being at leastabout 0.07% plus the amount required to combine with the columbium toform columbium carbide, and said one element being effective to increasesubstantially the amount of idiomorphic columbium carbide formed wherebysaid steel has improved resistance to abrasive wear.
 10. The abrasivewear resistant hot work steel set forth in claim 9 in which said oneelement is about 0.05% to 0.15% titanium.
 11. The abrasive wearresistant hot work steel set forth in claim 9 which said one element isabout 0.1% to 0.25% hafnium.
 12. Abrasive wear resistant deepair-hardening steel consisting essentially by weight of 0.4% to 1.2%carbon, about 0.5% to 2.5% manganese, about 0.5% to 1.5% chromium, about0.25% to 1.75% molybdenum, up to about 0.1% nitrogen, about 1.1% to 2.99columbium, at least one element selected from the group consisting of0.04% to 0.3% titanium, 0.05% to 0.5% zirconium, and 0.03% to 0.5%hafnium, the balance consisting essentially of iron and incidentalimpurities, the amount of carbon being at least about 0.07% plus theamount required to combine with the columbium to form columbium carbide,and said one element being effective to increase the amount ofidiomorphic columbium carbide formed whereby said steel has improvedresistance to abrasive wear.
 13. The abrasive wear resistant deepair-hardening steel set forth in claim 12 which contains about 1.1% to2.85% columbium.
 14. The abrasive wear resistant deep air-hardnEingsteel set forth in claim 13 in which said one element is 0.05% to 0.15%titanium.
 15. The abrasive wear resistant deep air-hardening steel setforth in claim 13 in which said one element is 0.05% to 0.2% zirconium.16. The abrasive wear resistant deep air-hardening steel set forth inclaim 13 in which said one element is 0.1% to 0.25% hafnium.
 17. Theabrasive wear resistant deep air-hardening steel set forth in claim 14which contains about 2.5% to 2.85% columbium.
 18. The abrasive wearresistant deep air-hardening steel set forth in claim 15 which containsabout 2.5% to 2.85% columbium.
 19. The abrasive wear resistant deepair-hardening steel set forth in claim 16 which contains about 2.5% to2.85% columbium.
 20. Abrasive wear resistant high speed steel consistingessentially by weight of about 0.5% to 2.0% carbon, less than about 0.5%manganese, less than about 0.5% silicon, about 3.5% to 4.5% chromium, upto about 0.5% nickel, up to about 10.5% molybdenum, up to about 19%tungsten, about 0.75% to 5.5% vanadium, about 3% to 12% cobalt, up toabout 0.5% copper, about 1.1% to 2.99% columbium, up to about 0.1%nitrogen, at least one element selected from the group consisting of0.04% to 0.3% titanium, 0.05% to 0.5% zirconium and 0.03% to 0.5%hafnium, the balance consisting essentially of iron and incidentalimpurities, the columbium and some of the carbon forming columbiumcarbide, and said one element being effective to increase the amount ofidiomorphic columbium carbide formed whereby said steel has improvedresistance to abrasive wear.
 21. The abrasive wear resistant high speedsteel set forth in claim 20 which contains about 0.15% to 0.4% manganeseand about 0.15% to 0.4% silicon.
 22. The abrasive wear resistant highspeed steel set forth in claim 20 which contains 1.1% to 2.85%columbium.
 23. The abrasive wear resistant high speed steel set forth inclaim 22 in which said one element is about 0.05% to 0.15% titanium. 24.The abrasive wear resistant high speed steel set forth in claim 22 inwhich said one element is about 0.05% to 0.2% zirconium.
 25. Theabrasive wear resistant high speed steel set forth in claim 22 in whichsaid one element is about 0.1% to 0.25% hafnium.
 26. The abrasive wearresistant high speed steel set forth in claim 23 which contains about2.5% to 2.85% columbium.
 27. The abrasive wear resistant high speedsteel set forth in claim 24 which contains about 2.5% to 2.85%columbium.
 28. The abrasive wear resistant high speed steel set forth inclaim 25 which contains about 2.5% to 2.85% columbium.